Production of hybrids between western gray wolves and western coyotes

Abstract

Using artificial insemination we attempted to produce hybrids between captive, male, western, gray wolves (Canis lupus) and female, western coyotes (Canis latrans) to determine whether their gametes would be compatible and the coyotes could produce and nurture offspring. The results contribute new information to an ongoing controversy over whether the eastern wolf (Canis lycaon) is a valid unique species that could be subject to the U. S. Endangered Species Act. Attempts with transcervically deposited wolf semen into nine coyotes over two breeding seasons yielded three coyote pregnancies. One coyote ate her pups, another produced a resorbed fetus and a dead fetus by C-section, and the third produced seven hybrids, six of which survived. These results show that, although it might be unlikely for male western wolves to successfully produce offspring with female western coyotes under natural conditions, western-gray-wolf sperm are compatible with western-coyote ova and that at least one coyote could produce and nurture hybrid offspring. This finding in turn demonstrates that gamete incompatibility would not have prevented western, gray wolves from inseminating western coyotes and thus producing hybrids with coyote mtDNA, a claim that counters the view that the eastern wolf is a separate species. However, some of the difficulties experienced by the other inseminated coyotes tend to temper that finding and suggest that more experimentation is needed, including determining the behavioral and physical compatibility of western gray wolves copulating with western coyotes. Thus although our study adds new information to the controversy, it does not settle it. Further study is needed to determine whether the putative Canis lycaon is indeed a unique species.

Figure 1. Number of litters and litter sizes of western, coyote pups produced at the U S. Department of Agriculture Wildlife Services National Wildlife Research Center Predator Research Facility between 2005–2012.

Figure 2. Three 6–7-month-old, littermate, F₁ hybrids between a male, western, gray wolf and a female, western coyote resulting from artificial insemination.

Figure 3. Facial view of two 6–7-month-old F₁ hybrids between a male, western, gray wolf and a female, western coyote resulting from artificial insemination.

Figure 4. Side view of a 6–7-month-old F₁ hybrid between a male, western, gray wolf and a female, western coyote resulting from artificial insemination.